1. Field of the Disclosure
The present disclosure relates to electronic devices and processes, and more particularly, to electronic devices that include non-volatile memory devices and processes for forming and using the same.
2. Description of the Related Art
Floating gate non-volatile memories (“FG NVM”) are commonly used in many applications. The two most common types of programming mechanisms for FG NVM include Fowler-Nordheim tunneling and hot carrier injection. Fowler-Nordheim tunneling is efficient but relatively slow. Efficiency can be measured by dividing the number of carriers that enter a floating gate by the number of carriers that enter a memory cell having the floating or the other storage element(s). The latter number can be approximated by using the product of the programming current and the programming time.
Hot carrier injection can include conventional hot carrier injection and source-side injection. Both involve the generation of hot carriers, some of which are injected into the floating gate or the other storage element(s). In conventional hot carrier injection when using a floating gate, an electrical field is generated along a channel region of a memory cell. Within the channel region, the electrical field is the highest near the drain region. The electrical field accelerates carriers flowing within the channel region, such that, within the channel region, the carriers are traveling the fastest near the drain region. A fraction of carriers having energies large enough to overcome the dielectric barrier are hot carriers. A small fraction of these hot carriers scatter within the channel region, and they are attracted by an electrical field generated by the control gate electrode, which can help inject some into the floating gate through a dielectric region separating the channel from the floating gate. Conventional hot carrier injection has a high programming current and is inefficient.
Source-side injection is a popular compromise, with respect to efficiency and programming current, between Fowler-Nordheim tunneling and conventional hot carrier injection. With source-side injection, hot carriers are still generated; however most of the hot carriers are generated within a portion of the channel region that is spaced apart from the drain region. Memory cells designed for programming by source-side injection are not without problems. Typically, the memory cells require one or more additional critical lithographic sequences and result in larger memory cells. As such, high-density floating gate memories are becoming more difficult to fabricate in commercial volumes.
Accordingly, there continues to be a need in the industry for memory cells having alternate designs, particularly memory cells that utilize injection techniques and are capable of providing improved channel structures, efficiency, and programming current responsiveness as well as read current responsiveness.
The use of the same reference symbols in different drawings indicates similar or identical items.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the disclosure.